Diabetes, one of the most insidious of the major diseases, can strike suddenly or lie undiagnosed for years while attacking the blood vessels and nerves. Diabetics, as a group, are far more often afflicted with blindness, heart disease, stroke, kidney disease, hearing loss, gangrene and impotence than non-diabetics, and diabetes and its complications are a leading cause of death in this country.
Diabetes adversely affects the way the body uses sugars and starches which, during digestion, are converted into glucose. Insulin, a hormone produced by the pancreas, makes the glucose available to the body""s cells for energy. The net effect of insulin is to promote the storage and use of carbohydrates, protein and fat. Insulin deficiency is a common and serious pathologic condition in humans. In Type I diabetes the pancreas produces little or no insulin, and insulin must be injected daily for the survival of the diabetic. In Type II diabetes the pancreas produces insulin, but the amount of insulin is insufficient and/or less than fully effective due to cellular resistance. In either form there are widespread abnormalities, but the fundamental defects to which the abnormalities can be traced are (1) a reduced entry of glucose into various xe2x80x9cperipheralxe2x80x9d tissues and (2) an increased liberation of glucose into the circulation from the liver (increased hepatic glucogenesis). There is therefore an extracellular glucose excess and an intracellular glucose deficiency. There is also a decrease in the entry of amino acids into muscle and an increase in lipolysis. These defects result in elevated levels of glucose in the blood, and prolonged high blood sugar.
Obesity and insulin resistance, the latter of which is generally accompanied by hyperinsulinemia or hyperglycemia, or both, are hallmarks of Type II diabetes. Despite decades of research related to these serious health problems, the etiology of type II diabetes is unknown.
As part of an ongoing study to identify genes which contribute to the risk of type II diabetes, association tests with polymorphisms within genes of biological interest were performed. One such gene, the gene encoding protein kinase C zeta (see FIGS. 1A-1B), was found to contain two common polymorphisms within its coding region. Work described herein has demonstrated an association of at least one of these polymorphisms with type II diabetes. Specifically, this work has identified an approximately 60% decrease in risk associated with the rare version (a C at position 246 (which is a T in the more common version)) of this polymorphism (significant to a p value of 0.002). Such an association has not previously been described.
Furthermore, the data suggest that the actual mutation influencing disease is not one of the two identified polymorphisms but rather that these polymorphisms may be reflecting the nearby action of another mutation which is in linkage disequilibrium with the SNP(s).
These results demonstrate a central role for the gene encoding PKC zeta in diabetes, and perhaps in related disorders. Study of the altered function of the mutant gene may guide drug discovery efforts. Moreover, a diagnostic test can be developed based on one or both of the mutations and/or the as-yet unidentified mutation to guide patient treatment. Thus, the invention relates to the SNPs identified as described herein, as well as to the use of these SNPs and others nearby in linkage disequilibrium with the identified SNPs for diagnosis, prediction of clinical course and treatment response, development of new treatments based upon comparison of the variant and normal versions of the gene or gene product, and development of cell-culture based and animal models for research and treatment. The invention further relates to novel compounds and pharmaceutical compositions for use in the diagnosis and treatment of such disorders.
The invention further relates to a method of diagnosing or aiding in the diagnosis of a disorder associated with the presence of a thymine at nucleotide position 246 of SEQ ID NO: 1 (e.g., diabetes) in an individual comprising obtaining a nucleic acid sample from the individual and determining the nucleotide present at nucleotide position 246 of SEQ ID NO: 1, wherein presence of a thymine at said position is indicative of increased likelihood of diabetes in the individual as compared with an appropriate control, e.g., an individual having a cytosine at said position. The invention further relates to a method of diagnosing or aiding in the diagnosis of a disorder associated with the presence of a thymine at nucleotide position 246 of SEQ ID NO: 1 (e.g., diabetes) in an individual comprising obtaining a nucleic acid sample from the individual and determining the nucleotide present at nucleotide position 246 of SEQ ID NO: 1, wherein presence of a cytosine at said position is indicative of decreased likelihood of diabetes in the individual as compared with an appropriate control, e.g., an individual having a thymine at said position.
In one embodiment, the invention relates to a method for predicting the likelihood that an individual will have diabetes (or aiding in the diagnosis of diabetes), comprising the steps of obtaining a DNA sample from an individual to be assessed and determining the nucleotide present at nucleotide position 246 of the PKC zeta gene. The presence of a xe2x80x9cCxe2x80x9d (the variant nucleotide) at position 246 indicates that the individual has a lower likelihood of having diabetes than an individual having a xe2x80x9cTxe2x80x9d at that position, or a lower likelihood of having severe symptomology. In a particular embodiment, the individual is an individual at risk for development of diabetes.
In another embodiment, the invention relates to pharmaceutical compositions comprising a variant PKC zeta gene product for use in the treatment of diabetes and related disorders. The invention further relates to the use of compositions (i.e., agonists and antagonists) which enhance or increase or which reduce or decrease, respectively, the activity of a variant PKC zeta gene product for use in the treatment of diabetes. The invention also relates to the use of a nucleic acid molecule encoding a variant PKC zeta gene product for use in the treatment of diabetes.